This work continues a program aimed at tracing neural systems which function to regulate sodium appetite. The current work is primarily structural in its emphasis on elucidating the brain structures which are necessary for this drive and is viewed as preliminary to detailed functional studies following a more comprehensive elucidation of general underlying neuroanatomical systems. It is becoming clear that a number of specific anatomically related structures in the forebrain, hypothalamus, thalamus, and lower brain stem tegmentum have important functions in the control of closely related drives such as sodium appetite, thirst and hunger. Sodium appetite has proven especially amenable to laboratory investigation and is used as a model system in the present studies. These studies utilize methods of destroying specific brain structures and determining whether there are resultant abnormalities in the ability to regulate salt intake in response to induced changes in body fluid volume and composition. The techniques of sterotaxic induction of lesions, histologic analysis and behavioral testing have been perfected to a degree at which they allow highly detailed analyses with very little uncontrolled variability. In addition, neuroanatomical techniques for tracing degenerated axons are used for determining the neural connections of relevant structures. This is done to help elucidate the relations between receptor, motivational and motor mechanisms of the appetitive system.